1. Field of the Invention
The present invention relates to an image processing apparatus configured to generate a reduced image of an endoscopic image.
2. Description of the Related Art
There are various types of the sizes of imaging devices (e.g., CCD, CMD, and CMOS) to be used in endoscopes. The sizes thereof are greatly different from each other depending, for example, on the differences among organs/parts to be observed, or the differences among the sizes/functions of endoscopes. When a narrow lumen, such as a bronchial tube or a biliary tract, is observed, an endoscope having a small diameter, in which an imaging device with a small number of pixels is mounted, is used. Additionally, in order to find a pathological change in an esophagus, stomach, large intestine, or the like, endoscopes of various sizes whose diameters range from a small one to a large one are used, and various imaging devices with pixels whose numbers range from a small one to a large one are mounted therein in accordance with the sizes. In an endoscope of a large size, there is generally room in the space of the tip portion thereof, and hence it is possible to mount an imaging device with a large number of pixels in which priority is placed on image quality.
When an organ/part to be observed is observed in detail, an endoscope, in which an imaging device with a large number of pixels is mounted, is used. On the other hand, when an organ/part is treated, or the like, an endoscope in accordance with the purpose of the treatment is used. In the former case, priority is placed on the capturing of an image with high quality and high resolution. In the latter case, priority is placed on the members for treatment, such as the diameter of a channel for making a treatment tool pass through, the number of the channels, or a water-jet function, and hence the size of an imaging device becomes relatively small. Thus, various imaging devices whose numbers of pixels and sizes are different from each other are used in endoscopes in accordance with design conditions based on the functions to be required.
Further, with the development of techniques, the number of pixels of an imaging device to be used in an endoscope is being increased. In the meantime, old model endoscopes are also usually designed to maintain compatibility with new system camera control units (CCUs: Camera Control Units) so as to be capable of being connected thereto. Although 20 years or more have passed since endoscopic images were videoized, three-generation old endoscopes can also be connected to new system CCUs. In such situations, when several-generation old endoscopes are compared with the latest ones, there are large differences between the numbers of pixels of imaging devices, in which the latest endoscopes have 10 to 20 times larger numbers of pixels.
An image captured by an endoscope is converted into an image for being displayed or recorded (hereinafter, appropriately referred to as an observation recorded image) by a CCU. An observation recorded image is typically generated by enlarging an image captured by an endoscope. Further, index images (they may be referred to as thumbnail images) are generated by reducing observation recorded images in order to be displayed in a list format. Each of the observation recorded image and the index image is typically generated to have a fixed size.